Answer: Create a lookup from the unusable fraction format to one that you can use in excel:
First column in the lookup should be the fraction in unusable format
Second column should be the fractions in a usable format, first format the cells in second column > Format Cells menu > Number tab > Category as Fraction > Type "Up to one digit (1/4)"
Manually in the corresponding cells the equivalent values (for example, below in cell H2 write 5/8)
Explanation: